Powertrains having an internal combustion engine coupled to a variator of continuously or infinitely variable transmission (CVT) may be employed to provide tractive effort in vehicles. A variator is capable of continuously changing an output/input speed ratio over a range between a minimum (underdrive) ratio and a maximum (overdrive) ratio, thus permitting infinitely variable selection of engine operation that achieves a preferred balance of fuel consumption and engine performance in response to an output torque request.
Known chain-type variators may be composed of two pulleys with a continuous belt or chain running therebetween, wherein sheaves of each of the pulleys sandwich the chain. Frictional engagement between the sheaves of the pulleys and the chain couples the chain to each of the pulleys to transfer torque from one pulley to the other. One of the pulleys may operate as a drive or input pulley and the other pulley may operate as a driven or output pulley. The speed ratio may be changed by urging the two sheaves of one of the pulleys closer together and urging the two sheaves of the other pulley farther apart, causing the chain to ride higher or lower on the respective pulley.